belfem::material::BhCurve Class Reference

B-H curve for ferromagnetic materials. More...

#include <cl_BhCurve.hpp>

Inheritance diagram for belfem::material::BhCurve:

Public Member Functions
	BhCurve (const string &aPath, const string &aLabel)
	Constructor - records the database path and group label.
virtual	~BhCurve ()=default
	Virtual destructor ( the concrete curve owns and deletes its splines ).
virtual real	nu (const real B) const
	Reluctivity ν(B) = H/B.
virtual real	mu (const real H) const
	Permeability μ(H) = B/H.
virtual void	dmudH (const real H, real &mu, real &dmudH) const
	Permeability and its derivative with respect to H.
real	B (const real H) const
	Magnetic flux density from field intensity.
real	H (const real B) const
	Magnetic field intensity from flux density.

Protected Attributes
const proc_t	mCommRank
	MPI rank.
const string	mPath
	path where data file is located
const string	mLabel
	Material label for error messages.

Detailed Description

B-H curve for ferromagnetic materials.

Represents the magnetization curve B(H) and its inverse H(B) for ferromagnetic materials using cubic spline interpolation of tabulated data.

The curve provides:

• ν(B) = H/B: Reluctivity [A/(T·m)]
• μ(H) = B/H: Permeability [T·m/A]
• dμ/dH: Derivative of permeability for Newton iterations
• B(H): Magnetic flux density from field intensity
• H(B): Magnetic field intensity from flux density

For fields above saturation (B > Bsat or H > Hsat), the material behaves linearly with an offset due to saturation magnetization:

• B = μ₀·( H + Msat ) for H > Hsat
• H = ν₀·B − Msat for B > Bsat ( Msat = ν₀·Bsat − Hsat, in A/m )

Data file format (HDF5 database):

• aPath points to an HDF5 file that holds one group per material.
• aLabel selects the group (e.g. "RoxieIron", "SAE1010").
• Each group stores two serialized cubic splines, "bnur" ( ν(B) ) and "hnur" ( 1/μ(H) ), plus the scalars "bsat" and "hsat".

Usage (BhCurve is abstract; construct the concrete BhSplineCurve):

BhCurve* bh = new BhSplineCurve( "bhdata.hdf5", "RoxieIron" );
material->load_bh_curve(bh);  // Material takes ownership
 
// Later, in FEM assembly:
real H = material->H(B);  // field intensity at |B| through the curve
                          // ( reluctivity itself is bh->nu(B); Material::nu() is Poisson's ratio )

See also

BELFEM Materials Module - Usage Guide

Constructor & Destructor Documentation

BhCurve()

belfem::material::BhCurve::BhCurve	(	const string &	aPath,
		const string &	aLabel )

Constructor - records the database path and group label.

Parameters

aPath	Path to the HDF5 database file (e.g. "bhdata.hdf5")
aLabel	Group name to load (e.g. "RoxieIron")

The concrete BhSplineCurve opens the HDF5 file, selects the group named aLabel and reads the pre-computed cubic splines "bnur" ( ν(B) ) and "hnur" ( 1/μ(H) ) together with the saturation scalars "bsat" and "hsat"; Msat is derived from these.

~BhCurve()

virtual belfem::material::BhCurve::~BhCurve ( )

virtualdefault

Virtual destructor ( the concrete curve owns and deletes its splines ).

Member Function Documentation

B()

real belfem::material::BhCurve::B ( const real H ) const

inline

Magnetic flux density from field intensity.

Parameters

H	Magnetic field intensity magnitude [A/m]

Returns

Magnetic flux density B [T]

Convenience function: B = μ(H) · H

dmudH()

void belfem::material::BhCurve::dmudH ( const real H, real & mu, real & dmudH ) const

virtual

Permeability and its derivative with respect to H.

Parameters

	H	Magnetic field intensity magnitude [A/m]
[out]	mu	Permeability μ(H) [T·m/A]
[out]	dmudH	Derivative dμ/dH [T·m/A²]

Computes both μ and dμ/dH efficiently for Newton-Raphson iterations in nonlinear magnetic FEM solvers.

For H < Hsat: Uses spline evaluation and derivative For H ≥ Hsat: Analytical formulas for linear regime

Reimplemented in belfem::material::BhSplineCurve.

H()

real belfem::material::BhCurve::H ( const real B ) const

inline

Magnetic field intensity from flux density.

Parameters

B	Magnetic flux density magnitude [T]

Returns

Magnetic field intensity H [A/m]

Convenience function: H = ν(B) · B

mu()

real belfem::material::BhCurve::mu ( const real H ) const

virtual

Permeability μ(H) = B/H.

Parameters

H	Magnetic field intensity magnitude [A/m]

Returns

Permeability μ [T·m/A]

For H < Hsat: Uses cubic spline interpolation For H ≥ Hsat: Returns μ₀·(1 + Msat/H)

Reimplemented in belfem::material::BhSplineCurve.

nu()

real belfem::material::BhCurve::nu ( const real B ) const

virtual

Reluctivity ν(B) = H/B.

Parameters

B	Magnetic flux density magnitude [T]

Returns

Reluctivity ν [A/(T·m)]

For B < Bsat: Uses cubic spline interpolation For B ≥ Bsat: Returns ν₀ - Msat/B (linear + offset)

Reimplemented in belfem::material::BhSplineCurve.

Member Data Documentation

mCommRank

const proc_t belfem::material::BhCurve::mCommRank

protected

MPI rank.

mLabel

const string belfem::material::BhCurve::mLabel

protected

Material label for error messages.

mPath

const string belfem::material::BhCurve::mPath

protected

path where data file is located

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The documentation for this class was generated from the following files:

• src/physics/materials/cl_BhCurve.hpp
• src/physics/materials/cl_BhCurve.cpp